1. Field of the Invention
The present invention relates generally to medical devices useful for measuring the diameter and pressure of a balloon occluder deployed within a vessel. More particularly, the devices provide information on when the balloon occluder engages the vessel wall, diameter of the vessel wall, and force exerted on the vessel wall.
2. Background of the Invention
Balloon occlusion devices are commonly deployed within a vessel during various cardiovascular surgeries to provide isolation of blood flow. During conventional or minimally invasive surgeries, including coronary artery bypass grafting, heart valve repair or replacement, septal defect repair, pulmonary thrombectomy, atherectomy, aneurysm repair, aortic dissection repair and correction of congenital defects, for example, circulatory isolation of the coronary blood flow from the peripheral vascular system is often required to establish cardiopulmonary bypass. Instead of using the traditional methods of aortic clamping, a balloon occluder is sometimes used to isolate blood flow in the aorta. Presently, balloon occluders are built to expand to the approximate lumenal diameter of the vessel, i.e., a balloon occluder with a smaller diameter would be used for the carotid artery while larger balloons are used in the aorta. Balloon occlusion devices are also used in other nonvascular procedures, such as dilation of an esophageal stricture in patients with achalasia, or dilation of an intra and/or extrahepatic bile duct in patients with biliary stenosis.
There are several disadvantages associated with the current methods of inflating a balloon occluder in a vessel or body cavity. First, the optimal size of the balloon occluder for occluding the lumen of the vessel or the body cavity is unknown and is usually estimated according to the average lumenal diameter. The vessel may be affected by atherosclerosis, and the actual lumenal diameter may be reduced. Second, as the balloon is inflated to occlude the lumen of the vessel or body cavity, the point of contact of the perimeter of the balloon with the wall of the vessel or body cavity is uncertain. The operator can only estimate an acceptable level of wall distention. Third, the pressure generated by the expanded balloon on the wall of the vessel or body cavity is unknown. Complications due to over-inflation of the balloon may occur, including (1) atherosclerotic plaque rupture leading to distal embolization, (2) dissection of the vessel wall, (3) pseudoaneurysm formation due to subintimal hemorrhage, (4) aneurysm formation due to hyperextension and weakening of the vessel wall, (5) diverticulum formation due to weakening of the body tissue, and (6) vessel wall rupture or organ perforation.
New devices and methods are thus needed for balloon occlusion of a vessel or body cavity, in order to provide information on the effective diameter of the vessel or body cavity and allow an operator to optimally control the inflation of the balloon without damage to the vessel wall or body tissue.
The invention provides devices and methods for controlling the inflation of balloon occlusion devices. One embodiment of the devices includes first and second balloons. The first balloon is adapted for insertion into a patient""s vessel or body cavity. The balloons may be elastomeric or non-elastomeric balloons. Each of the two balloons communicates with an inflation lumen. Each inflation lumen communicates independently with a pump for inflating the balloon. Both lumens communicate with a differential pressure gauge, which measures the pressure inside each balloon, compares both pressures, and displays the information.
In another embodiment, the pumps are syringes, which are adapted for infusion of air or fluid into the balloon. The syringes may operate in tandem for inflating the balloons simultaneously. In still another embodiment, the pressure gauge includes a shut-off valve, operably associated with the second inflation lumen. The valve enables the pressure gauge to terminate inflation into the second lumen and balloon after the pressure in the first balloon exceeds a certain threshold. In certain embodiments, the gauge may include a pressure limiter which limits the pressure in the first balloon from exceeding a set threshold, thereby avoiding over-inflation of the first balloon inside the vessel or body cavity.
The invention provides methods for measuring the pressure of a balloon occluder deployed in a patient""s vessel or body cavity, e.g., bile duct. In a first method, using the devices described above, the first balloon is inserted through an incision into the lumen of a patient""s vessel, e.g., aorta, or body cavity while maintaining the second balloon outside the patient""s body. The first and second balloons are inflated simultaneously at the same rate of inflation by operating the pumps, which infuse air or fluid into the inflation lumens. The pressure within the first and second balloons are measured and compared by the differential pressure gauge, which comparison indicates when the first balloon engages the lumenal wall of the vessel or body cavity. As the first balloon contacts the vessel wall, the pressure in the first balloon rises disproportionately compared to the second balloon. The operator may then terminate inflation in the first balloon to avoid over-inflation.
In another method, when the pressure in the first balloon exceeds the pressure in the second balloon, the pressure gauge may activate the shut-off valve, thereby terminating the inflation of the second balloon. The gauge may be reset to measure the pressure within the first balloon and the atmosphere. In this way, any increase in the pressure in the first balloon is caused by the resistance of the vessel wall against the expanding balloon. The less compliant the vessel, e.g., artery with atherosclerotic plaque, the higher the resistance of the vessel wall and the higher the pressure registered in the pressure gauge. In the embodiment where the pressure gauge includes a pressure limiter, the limiter may sound an alarm when the pressure in the first balloon exceeds a set threshold, thereby avoiding complications associated with over-inflation of the balloon occluder.
It will be understood that there are several advantages to using the balloon occlusion measuring devices and methods disclosed herein. For example, the devices (1) notify the physician when the balloon contacts a vessel wall, (2) provide information on the diameter of the vessel wall, (3) provide information on pressure exerted on the vessel wall, (4) can be employed in any vessel with or without stenosis, (5) can be employed to occlude or dilate a body cavity, and (6) minimize complications associated with over-inflation of the balloon occluder, i.e., wall rupture, dissection, pseudoaneurysm, and/or embolization.